This invention relates to novel compositions comprising mixtures of two herbicides and to a method of controlling undesired vegetation in the growth of upland cereal and rice crops by the application of an effective amount of one of the herbicides that comprise the mixture, alone or the composition comprising the mixture.
New compounds effective for controlling the growth of undesired vegetation are in constant demand. In the most common situation, such compounds are sought to selectively control the growth of weeds in useful crops such as cotton, rice, corn, wheat and soybeans, to name a few. Unchecked weed growth in such crops can cause significant losses, reducing profit to the farmer and increasing costs to the consumer. There is especially a need for finding compounds that selectively control the growth of undesired vegetation in growing rice. Rice is a staple crop for millions of people of the world whose diet depends on its availability. There are many products commercially available for such purposes, but the search continues for products which are more effective, less costly and environmentally safe.
The "sulfonylurea" herbicides are an extremely potent class of herbicides discovered within the last few years. A multitude of structural variations exist within this class of herbicides, but they generally consist of a sulfonylurea bridge, --SO.sub.2 NHCONH--, linking two aromatic or heteroaromatic rings.
Rice and upland cereals such as wheat, barley, oats etc. satisfy the food need of a large portion of the world's population. The continued population increase and concomitant food shortage increase the need for improvements in the production of such crops. Improving the efficiency of producing such crops by controlling undesirable weeds through the application of herbicides is continually being sought. Along with this improvement the application of herbicides to crops such as rice and wheat without injury thereto is also being sought.
The compound N-(3,4-dichlorophenyl) propionamide (propanil) has been found very effective for controlling weeds in rice crops. U.S. Pat. No. 3,382,280 discloses herbicidal propanil.
U.S. Pat. No. 4,394,506 discloses compounds within the scope of Formula I of the present invention.
U.S. Pat. No. 4,383,113 also discloses compounds within the scope of Formula I of the present invention.
U.S. Pat. No. 4,645,527 discloses the use of certain sulfonamides to protect cereal crops from injury by compounds within the scope of Formula I of the present invention where X is CH.sub.3, Y is OCH.sub.3 and Z is N.
U.S. Pat. No. 3,816,092 discloses a method for applying propanil to obtain a herbicidal effect.
There is, however, no disclosure in any of the above references of the use of the compounds they describe for control of vegetation with safety to rice or in the combination disclosed herein.